leptos-use/docs/book/src/server_side_rendering.md

Server-Side Rendering

When using together with server-side rendering (SSR) you have to enable the feature ssr similar to how you do it for leptos.

In your Cargo.toml file add the following:

...

[features]
hydrate = [
    "leptos/hydrate", 
    ...
]
ssr = [
    ...
    "leptos/ssr",
    ...
    "leptos-use/ssr" # add this
]

...

Please see the ssr example in the examples folder for a simple working demonstration.

Many functions work differently on the server and on the client. If that's the case you will find information about these differences in their respective docs under the section "Server-Side Rendering". If you don't find that section, it means that the function works exactly the same on both, the client and the server.

Functions with Target Elements

A lot of functions like use_resize_observer and use_element_size are only useful when a target HTML/SVG element is available. This is not always the case on the server. If you use them with NodeRefs they will just work in SSR. But what if you want to use them with window() or document()?

To enable that we provide the helper functions use_window() and use_document() which return a new-type-wrapped Option<web_sys::Window> or Option<web_sys::Document> respectively. These can be used safely on the server. The following code works on both the client and the server:

use leptos::*;
use leptos::ev::keyup;
use leptos_use::{use_event_listener, use_window};

use_event_listener(use_window(), keyup, |evt| {
    ...
}); 

There are some convenience methods provided as well, like use_document().body() which just propagate a None on the server.